In an automotive powertrain, a transmission output shaft transmits rotational force or torque from the transmission to one or more drive shafts or axles in order to propel the vehicle. Vehicles equipped with front-wheel or all-wheel drive systems are generally equipped with constant velocity (CV) joints, which allow the vehicle to more efficiently transmit torque from a rotating output shaft to a drive shaft or shafts through a range of joint operating angles, such as are experienced while the vehicle is turning. CV joints may take the form of, for example, ball joints, universal or U-joints, and/or tripot joints.
The locus of engagement, or shaft interface, formed or positioned between of a pair of rotating shafts, or between a rotating output shaft and a CV joint, may be exposed to a substantial amount of debris and other environmental contaminants. Debris may take the form of water, dirt, and/or oil from a road surface or that is discharged from the vehicle powertrain. Therefore, a flexible shaft or axle seal is typically used to protect the shaft interface, thereby preventing this debris from entering the transmission, where it may potentially damage the gears or other transmission components. The shaft seal also serves to retain special gear oil within the transmission case, as the loss of gear oil around or through a damaged or worn shaft seal may adversely affect the performance of the transmission.
Shaft seals may include a thin, stamped metal carrier, to which is bonded or attached a flexible rubber or polymeric sealing material having a one or more sealing lips. The sealing lips are typically shaped or adapted to seal against a radially outward surface of an output shaft sleeve, which is press-fitted into the drive shaft or half shaft to rotate in conjunction therewith. The stamped metal carrier allows the seal to be press-fitted into the stationary transmission case, and also provides some level of protection to the sealing material. However, such sealing devices may be less than optimal depending on the amount of foreign debris and/or ensuing corrosion or chemical attack thereto as the debris attacks the exposed surfaces of the seal.